Do not integrate a single bird to an established flock. That is a recipe for a disaster. What you want to do, is introduce her to a single bird, then later introduce the pair to the flock. You can get her in there, but it takes a lot of fiddling around.
First, let all the others out for the day. Lock the new one in by herself into the coop/run. This will allow her to explore, find the feed stations, the hide outs calmly without being chased for her life. At night, put her in a dog crate, let the others in roost in the coop.
Day two - repeat
Day three - pick a middle of the flock bird. Not the top birds, and not the bottom birds. If you don't know, walk out aways, toss down a treat. First birds are top, last ones are bottom, get one bird out of the middle.
Let out the birds, except for the middle bird and the new bird. They get locked in the coop/run. There will probably be a dust up or two, but one on one, won't be too bad and should settle pretty quickly. This is MUCH better one on one, than 6 to one. Rinse repeat, keeping this pair together.
Then, as close to dark as possible let the others in to go to roost. Get down there early in the morning and check on them frequently on that day.
Mrs K